While the majority of earthmoving vehicles use a conventional steering wheel system, a few have incorporated a control mechanism using a substantially vertical control handle of the cylindrical joy-stick type for steering purposes. In such construction the control handle can be pivoted by an operator's left hand to effect a left turn when it is rocked to the left, and a right turn when it is rocked to the right in a substantially vertical and transversely oriented plane.
In one control mechanism offered by VME Industries Sweden AB, of Eskilstuna, Sweden, an actuator element located adjacent to the steering control handle can be switched between an active mode wherein the control handle can effect steering, and an inactive mode wherein a conventional steering wheel can effect steering and the control handle is disabled. In that mechanism a three-way rocker switch is located next to the steering control handle that can be manipulated to obtain forward and reverse movement of the vehicle, and another actuator element near the rocker switch can be depressed to force the transmission to shift down to first gear. Such a widely dispersed arrangement of the actuating elements makes it inconvenient for the operator. Not only is it fatiguing, but also the operator's reaction time is slower since his hand must travel from one actuating element to another.
One other control mechanism offered by Engstrom & Nilson Maskin AB of Jupitervagen 10, Sweden, incorporates a generally cylindrical, upright control handle that is rockable in a transverse plane to effect steering, and a three-way rocker switch located at the top thereof to effect forward and reverse operation of the vehicle. However, that placement of the rocker switch is relatively inconvenient, and there is no provision at the control handle for shifting the gear ratios of the associated transmission. That system uses a conventional steering wheel for high speed travel and simultaneous disabling of the control handle's steering capability.
In a further multi-purpose control offered by Liebherr International AG, of Bulle, Switzerland, or one of its subsidiaries, an upstanding control handle could be pivotally rocked in a transverse plane to the left or to the right in order to obtain the rack-back of a bucket or the dumping of the bucket, and could be pivotally rocked in a longitudinal plane to raise the lift arms or to lower the lift arms supporting the bucket. In addition, twisting of that control handle about its own vertical axis would cause a speed selection between the first, second, and third gear ratios of the transmission of the vehicle. Moreover, a three-way rocker switch on the front portion of the control handle and facing away from the operator could be manipulated to obtain forward and reverse travel of the vehicle. That servo-actuated joystick control is independent of the vehicle's steering control mechanism.
Historically, single lever control mechanisms have incorporated complex mechanical linkages with too many operating joints, or a plurality of cables to achieve the desired multiple operating functions.
Accordingly, what is desired is a simple, yet rugged and economical steering and transmission shifting control mechanism for operating a vehicle that will use an upright and rockable control handle for the steering function, and will incorporate a more convenient actuating element in close association with the control handle for effecting a speed change function of the associated multi-speed transmission. Preferably, another actuating element should also be closely associated with the control handle for effecting a directional change of that transmission. Furthermore, the control mechanism should be easy to assemble or service, and the various actuating elements should be so constructed and arranged relative to the control handle that the principles of economy of motion of an operator's hand are fully employed. In this way operator fatigue can be minimized because the displacement of the control handle and associated actuating elements is natural relative to the operating function achieved.
The present invention is directed to overcoming one or more of the problems as set forth above.